1. Field of the Invention
The present invention concerns a seal tester.
2. Description of the Prior Art
Refrigerator compressors, evaporators, SF6 circuit-breaker pole-pieces and the like are often seal tested by placing them in a vacuum chamber connected to a helium leakage detector and filling the device under test with helium or an air-helium mixture.
If there is any leak, the helium escapes and its flowrate is measured by the detector.
In this seal testing method the device under test is filled with the tracer gas through a pipe which passes through the vacuum chamber and which comprises at its end a coupling to be connected to the device under test.
One conventional coupling comprises a female part which is mounted at the end of a pipe connected to the device under test and a male part which is mounted on the test gas feed pipe, the two parts nesting one within the other. The interfaces between each part and the respective pipe and between the two parts incorporate seals. These seals must provide a perfect seal, must be impermeable to the test gas (helium) and must be able to withstand thousands of compression and decompression tests, couplings and uncouplings. These requirements are difficult to meet and it is therefore necessary to change the seals frequently, which involves dismantling the couplings.
An object of the invention is to avoid the need for frequent replacement of the seals by eliminating the need for a perfect seal at the couplings.